The goal of this research is to elucidate the critical cellular changes that lead to irreversible cell injury. These mechanisms must be understood before rational interventions can be proposed. We have focused on ionic and energetic changes that occur during many types of cell injury. Our previous studies using NMR methods have shown a crucial role for ionic alterations, particularly the level of cytosolic calcium, in the development of cell injury. We have found that any injury that reduces cell ATP will cause an increase in H(+) associated with the increased glycolytic activity, which in turn results in increased Na(+) and Ca(2+) via Na/H and Na/Ca exchange. In many systems, it has been observed that exposure of cells or animals to a brief stress provides considerable protection against a subsequent more severe stress. This brief period of stress is known to result in the synthesis of heat shock and stress proteins; however, in spite of the identification of these proteins, there is still little understanding of the mechanism of protection. We have begun to examine ionic and metabolic changes that are induced by brief periods of stress which could afford subsequent protection. Exposing perfused rat heart to several brief (5 minute) periods of anoxic stress (referred to as preconditioning) affords protection when these preconditioned hearts are subjected to a longer period (30 minutes) of anoxic stress such that the preconditioned hearts have less necrosis and better recovery of function compared to controls. We have identified some interesting ionic and metabolic changes in these preconditioned hearts. For example, during the severe anoxic stress (30 minutes) the preconditioned hearts exhibit a reduced rise in H(+), Na(+), and Ca(2+) . Since a rise in Ca(2+) is associated with increased cell injury, this lessening of the rise in Ca(2+) could be an important protective mechanism. We are beginning to explore the role of humoral factors such as adenosine in this effect, and find that very low levels of adenosine (10 micro-M) also reduce the rise in cell H(+), Ca(2+) and Na(+) during a severe anoxic stress. We are currently investigating the mechanisms by which preconditioning and adenosine reduce ionic changes.